The objectives of this project are: to establish sensory and pain thresholds to electrical tooth pulp stimulation in myofascial pain dysfunction (MPD) patients and to relate sub-sensory, sensory and pain producing stimuli of the tooth pulp to the masseteric inhibitory period in MPD patients, by means of electromyographic (EMG) recordings. In both these cases comparison between MPD patients to normal subjects will enable a better understanding of the MPD syndrome pain and dysfunction mechanisms, and the gain of insight into possible protective mechanisms of the inhibitory period.